Hitherto, there is a known feed water pipe which supplies cooling water into a steam generator such as a pressurized water reactor. In the feed water pipe, a thermal stratification phenomenon may occur due to vapor flowing into the pipe. The thermal stratification phenomenon is not desirable in that it causes a stress of a fatigue source. Further, when the vapor flowing into the pipe remains in the pipe after the supply of water is performed again, there is a possibility that water hammer occurs. The water hammer is not desirable in that it generates an impact on an inner pipe.
Patent Literature 1 discloses a technique of a feed water pipe of a steam generator in which a weir is attached to an inner upper wall of a feed water pipe bent to raise a water supply ring. Patent Literature 2 discloses a technique of a water supply and discharge pipe structure of a steam generator with a body and a heat exchange pipe group provided inside the body in which a plurality of horizontal outlet ports are bored in an upper pipe wall of a horizontal water supply ring provided in the upper portion inside the body and communicating with a feed water pipe outside the body.